[R] Reading Version 4 .sdd files

Prof Brian Ripley ripley at stats.ox.ac.uk
Mon Oct 4 21:05:07 CEST 2004

On Mon, 4 Oct 2004, John Chandler wrote:

> Dear R-Help,
> I've never had any trouble importing data into R until I had to import
> an .sdd file for a class. The file can be found here:
> http://www.math.umt.edu/steele/Math%20549/Farms.sdd. It begins with the
> line "## Dump S Version 4 Dump ##". I first attempted read.S which
> issued the message "not an S object". I then checked the Import/Export
> manual which seemed to indicate that data.restore might do the trick.

That manual says otherwise.

> Alas, it seems that function is trying to interpret the name of the data
> frame as an S mode or some such thing.
> Searched the archives (courtesy of Dr. Baron) and found this from Dr.
> Ripley: ".sdd files from S-PLUS 6.0 are
> S4 dumps, and will not work." This was written in 2002, is it still
> accurate? 

Yes.  It's right there on the help page for data.restore, twice!  It is
also in the `R Data Import/Export Manual' you cited.

> Right now my only obvious course of action is to get on a
> machine that has S+, read in this file and dump it in a more useful
> format. Are their others?

Not that I have ever heard of, at least not open to those who have no
access to S4 source code.  Whereas the S3 dump format has been disclosed, 
I don't believe that the S4 one has.

If this is an S4 class then you really want a dump of it, as R's internal 
representation is not at all like S4's, I believe.

Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595

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